The present invention relates to an apparatus for measuring a three-dimensional shape of an object and, more particularly, to an apparatus for measuring a three-dimensional shape and position of the object in a noncontact manner.
The noncontact technique is particularly important in the measurement with the object which is not easily accessible or is easily deformable by contact. In medical field, the object can be a living organism which is generally soft and easily cause undesirable reflex by contact. Noncontact measurement has been widely applied to a variety of fields such as parts assembly in an automated factory in industrial fields, in addition to the medical field.
Some three-dimensional noncontact measurement schemes utilize a parallax error, such as a stereoscopic photography, pattern projection, and a lightsection method. A shape of an object of interest can be accurately measured by these methods. However, since the object is observed from two different viewpoints, two or more input images are required, and making the correspondence between the two images is not an easy task even with the help of a computer. Other conventional three-dimensional measurement schemes using one observation image are also known and exemplified by texture analysis and a Moire method. However, with these techniques an absolute position and size of the object of interest cannot be measured directly, and many practical limitations are imposed on these methods.
The apparatus disclosed in U.S. Pat. No. 4,668,094 (issued May 26, 1987, assigned to the assignees of the present application) has a single view point and uses a single observation image. This apparatus, however, requires two pattern-projection devices. Therefore, it has been hoped that an apparatus would be developed which has a simpler structure, uses fewer elements, and is able to perform image processing more simply and at a higher speed.